Hearing test devices that monitor the condition within a human ear are known. Such test devices generally require that the person performing the test (the “operator”) place a test probe of the device within the ear canal of a test subject. Once the probe is placed properly within the ear canal, the operator activates the device, usually by pressing a button or the like. The device then emits test signals into the subject's ear through the probe in the ear canal. In response to the test signals emitted, the device receives response signals from the ear, likewise through the probe in the ear canal. Such response signals received are then used to determine whether the ear is functioning properly.
One such test device analyzes the distortion product otoacoustic emissions (DPOAE) generated by the ear to determine middle ear function. More specifically, a DPOAE test device generates and emits two audible tones (i.e., test signals) at different frequencies into the ear canal of a subject. A healthy ear will produce, in response to the two audible tones, a response signal having a frequency that is a combination of the frequencies of the two audible tones. Thus if the two audible tones generated have frequencies of f1 and f2, respectively, a healthy subject's ear will emit a response signal having a frequency that is a combination of f1 and f2. The strongest response signal occurs at a frequency of (2)(f1)-f2, and is referred to as the distortion product.
In addition, DPOAE test devices also generally modify the frequencies of the audible tones transmitted into the ear canal over time during the course of the test. In response, a healthy subject's ear will emit a distortion product having a frequency that similarly changes over time during the course of the test. Generally speaking, the lack of distortion product otoacoustic emissions from the ear during the course of the test is an indication of possible hearing loss.
Existing DPOAE test devices all use a probe that is inserted into the ear canal of the test subject. Such a probe is either attached to the device via a cable, or is mounted on the device to form an integrated hand-held device. In either case, proper placement of the probe into the ear canal is critical to obtaining accurate and useful DPOAE measurements. This is primarily due to the fact that otoacoustic emissions produced by a healthy ear are extremely small in magnitude, typically in the range from −10 dB SPL to +20 dB SPL. Improper placement of the test probe in the ear canal may result in the inadvertent masking of the emissions (and thus the triggering of a false negative response), in an inaccurate measurement, or in an otherwise invalid result. Proper placement of the test probe in the ear canal is generally determined by one or more of several factors. An operator may be required to insert the probe deeply into the ear canal and/or to create a seal between the probe and the ear canal. An operator may also be required to ensure that the probe is not blocked by a collapsed ear canal, by the canal wall itself, or by earwax. In addition, the operator may also be required to determine that, once the probe is inserted, the resulting volume of the ear canal is within a certain desirable range.
Consequently, it is often very difficult for an operator to know whether proper placement of the probe has been achieved before the operator initiates the testing process. Moreover, particularly in the case of an integrated hand-held device, the act of initiating the test (e.g., pressing a start button) may shift the placement of the probe in the ear canal, which in and of itself may cause an inaccurate measurement. As a result, an operator may be required to perform several tests in order to obtain accurate measurements, greatly slowing down the testing process.
In addition, in some cases, these problems may prevent an accurate measurement altogether. Specifically, a large proportion of DPOAE testing is performed on infants. Typically, the infant is asleep when the testing is performed so that movement (and thus noise) is minimal. The process of properly placing and positioning the probe into an infant's very small ear canal for the amount of time and number of iterations needed to obtain accurate results often wakes the infant, which often makes the test impossible to complete, particularly if the infant is crying.
Therefore, it is an object of the present invention to provide a test operator with an indication that the testing probe is properly placed within the test subject's ear canal.
It is also an object of the present invention to provide automatic initiation or starting of the test once the probe has been properly placed within the test subject's ear canal.